Heat transfer system for a co-generation unit

ABSTRACT

A heat exchange cooling system for an internal combustion engine co-generation plant, which allows exhaust recycled gas combustion while maintaining lower head temperatures to reduce thermal NO x  emissions while delivering increased process/utility heat to a proximate co-generation client, is provided. The cooling system has two cooling loops with different flow rates: one through the engine and the second through exhaust manifolds, such that higher engine block flow resulting in cooler head temperatures is provided, while allowing higher temperature coolant to flow through exhaust exchangers, such that when the two coolant flows converge at a process/utility heat exchanger for heating co-generation client liquid, the combined flows substantially increase the transferred heat. In another embodiment, a separate intercooler circuit is used to cool the compressed intake charge containing the recycled gas prior to entry into the intake engine manifold to further reduce head temperatures and control thermal NO x  emissions.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to heat transfer systemsfor co-generation units; and, more particularly, to heat transfer andcooling systems for internal combustion engine driven co-generationunits.

[0003] 2. Description of Related Art

[0004] Electric energy generation in this country has lagged behinddemand. There are a number of reasons for this, but chief among them isfailure of traditional energy producers to replace spent units andcapitalize new plants. This has been, in part, due to increased airquality regulations. In addition new challenges face electric generationsecurity. Events of Sep. 11, 2001 showed this nation its vulnerabilityto terrorist attack. Vital operations, such as police, medical and civildefense that relied upon the electric power “grid” for service, realizedthat their needs were susceptible to disruption and viewed stand-aloneunits as well as micro grids as a possible solution. These alternativesare fraught with their own problems. Chief among the reasons is adrastic increase in demand. Thus, while energy demand has increased,generating capabilities have not.

[0005] One reason for the growth in demand is the increased use ofcomputers and other technology for industrial and business purposes, aswell as personal use. As computer usage continues to grow, the use ofpower-consuming peripheral technologies, such as printers, cameras,copiers, photo processors, servers, and the like, keep pace and evenexpand. As business use of computer based equipment continues to rise,as do the number of in-house data servers, outsourced data storagefacilities, financial systems, and Internet-related companies requiringconstant electrical uptime and somewhat reducing traditional peak demandtimes, requirement for reliable, cheap, environmentally compliantelectrical power continues to grow.

[0006] Other technological advances have also increased electricalenergy demand. Increased use of power consuming devices in every aspectof life from medical to industrial manufacturing robots, as well asinnovations in almost every-research and industrial field are supportedby increasingly complex technology, which requires more electrical powerto function. CAT scans, NMRs, side looking X-rays, MRIs and the like alltake electrical power.

[0007] As a result, the Federal Government deregulated power generation,and a number of states have begun to establish competitive retail energymarkets. Unfortunately, the deregulation process has not providedadequate incentives for industry entities to construct generatingfacilities, upgrade the transmission grid, or provide consumers withprice signals to enable intelligent demand-side management of energyconsumption. With the deregulation in the utility market, energy (kWh)has become a commodity item that can be bought or sold. However, swingsin supply and demand leave end users open to fluctuations in the cost ofelectricity.

[0008] According to the ETA, to meet projected increases in demand overthe next 20 years, at least 393 GW of additional generating capacitymust be added. In some areas, the growth in demand is much higher thanthe projected two percent average (e.g., California's peak electricitydemand grew by 18 percent between 1993 and 1999, while generatingcapacity increased by only 0.3 percent.) Despite California's highlypublicized energy situation, a similar problem exists for other statesas well; the New York Independent System Operator recently stated that8600 MW of additional generating capacity (a 25 percent increase) mustbe added by 2005 to avoid widespread shortages that may lead toblackouts.

[0009] In addition to the mismatch between demand and generatingcapacity, the physical transmission infrastructure necessary to deliverpower from geographically remote generating facilities to the consumer'slocation is unable to support the increased load. Even under today'soperating conditions, the transmission grid is subject to stress andoccasional failure.

[0010] Additionally, security and reliability of source has become ofincreasing concern. Vulnerability of grid systems and blackouts havebecome more commonplace. Strategic industries are looking to cut energycosts, increase reliability, and assure security. This has lead to aninterest in distributed market technologies. The potential market fordistributed generation has become vast without adequate means forfulfilling this need. Again, inefficiency, reliability, andenvironmental concerns are major barriers. The compelling economics aremade on engine efficiency without the financial benefit of waste heatusage, yet with all of the same customer reluctance to accept hassles.Industry estimates indicate that the existing market for distributedgeneration is $300 billion in the United States and $800 billionworldwide.

[0011] The need to leverage existing technology while transitioning toalternative energy sources is an important driver for meeting thischallenge. Although most existing distributed generation sites use smallgas turbine or reciprocating engines for generation, there are manyalternatives that are being considered over the longer term.Technologies, such as micro turbines, are currently available, but onlyused at a relatively small number of sites. These newer generators offersome inherent advantages, including built-in communicationscapabilities. It is anticipated that fuel cells will be available in thenext five years, which will provide some highly appealing,environmentally friendly options.

[0012] As it stands today however, small gas turbine and reciprocatingengines comprise a substantial proportion of existing generatortechnology in the market and will for some time to come for a number ofreasons. Engines provide the best conversion efficiency (40%), and theycan operate using non-pressurized gas. Micro turbines, on the otherhand, require compressed gas and conversion efficiency is lower(approximately 30%). These latter generators tend to be used inwastewater and landfill and other specialty sites, where a conventionalprime mover is unable to stand up to poor fuel quality. Therefore, forutilities to truly benefit from a distributed generation scheme over theshort term, they must look to the existing generator technology toprovide a sustainable and affordable solution.

[0013] Waste heat utilization or co-generation is one way to meet thischallenge. In the case of power generation, the waste heat is not used,and the economics are based largely on the cost of the electricityproduced (i.e. heat rate is paramount), with little consideration forimproved reliability or independence from the electric grid. Theanticipated fluctuation in energy costs, reduced reliability, andincreasing demand has led end users to consider maximizing efficiencythrough use of heat from generation of on-site generating-heat capturesystems, i.e. co-generation, or “Combined Heating and Power” (CHP).

[0014] Co-generation of electricity and client process/utility serviceheat to provide space heating and/or hot water from the same unit is onesolution. Co-generation provides both electricity and usable process orutility heat from the formerly wasted energy inherent in the electricitygenerating process. With co-generation, two problems are solved for theprice of one. In either case, the electricity generation must meetstringent local air quality standards, which are typically much tougherthan EPA (nation wide) standards.

[0015] On-site co-generation represents a potentially valuable resourcefor utilities by way of distributed generation. A utility can increasecapacity by turning to a “host” site (e.g. industrial user) with anexisting generator, and allow them to parallel with the grid and usetheir generator capacity to handle peak volumes. From the utility'spoint of view, the key advantages to a distributed generation solutionare twofold: improved system reliability and quality; and the ability todefer capital costs for a new transformer station.

[0016] For customers who can use the process/utility waste heat, theeconomics of co-generation are compelling. The impediment to widespreaduse is reliability, convenience, and trouble-free operation.Co-generation products empower industrial and commercial entities toprovide their own energy supply, thus meeting their demand requirementswithout relying on an increasingly inadequate public supply andinfrastructure.

[0017] Unfortunately, to date, the most widespread and cost-effectivetechnologies for producing distributed generation and heat requireburning hydrocarbon-based fuel. Other generating technologies are inuse, including nuclear and hydroelectric energy, as well as alternativetechnologies such as solar, wind, and geothermal energy. However,burning hydrocarbon-based fuel remains the primary method of producingelectricity. Unfortunately, the emissions associated with burninghydrocarbon fuels are generally considered damaging to the environment,and the Environmental Protection Agency has consistently tightenedemissions standards for new power plants. Green house gases, as well asentrained and other combustion product pollutants, are environmentalchallenges faced by hydrocarbon-based units.

[0018] Of the fossil fuels, natural gas is the least environmentallyharmful. Most natural gas is primarily composed of methane andcombinations of Carbon Dioxide, Nitrogen, Ethane, Propane, Iso-Butane,N-Butane, Iso-Pentane, N-Pentane, and Hexanes Plus. Natural gas has anextremely high octane number, approximately 130, thus allowing highercompression ratios and broad flammability limits. A problem with usingnatural gas is reduced power output when compared to gasoline, duemostly to the loss in volumetric efficiency with gaseous fuels. Anotherproblem area is the emissions produced by these natural gas engines.Although, the emissions are potentially less than that of gasolineengines, these engines generally require some types of emissionscontrols such as exhaust gas re-circulation (EGR), positive crankcaseventilation (PCV), and/or unique three-way catalyst. A still anotherproblem with using natural gas is the slow flame speed, which requiresthat the fuel be ignited substantially before top dead center (BTDC). Ingeneral, most internal combustion engines, running on gasoline, operatewith a spark advance of approximately 35° F. BTDC; where as, the sameengine operating on natural gas will require an approximate advance of50° F. BTDC. The slower burn rate of the fuel results in reduced thermalefficiency and poor burns characteristics. Never the less natural gasfueled engines provide a valuable power source for distributedgeneration.

[0019] Internal combustion engines utilized for combined heat and powerare designed so that engine coolant from the radiator passes through aprocess/utility heat exchanger so the heat from combustion can betransferred to a co-generation client. Prior art co-generation systemsemploying internal combustion engines, and specifically, natural gasfueled engines have suffered from the myriad of problems includingelevated head temperatures and inability to deliver large quantities ofprocess and/or utility heat to the co-generation client. Excessive headtemperatures lead to inefficient operation and unacceptableenvironmental conditions, which include excessive use of fuel as well assignificant thermal NO_(x) production.

[0020] It is well known that emission reduction for natural gas enginescan be accomplished by recycling of exhaust gases to make the engines“run lean.” Numerous systems have been devised to recycle exhaust gasinto the fuel-air induction system of an internal combustion engine forthe purposes of pre-heating the air-fuel mixture to facilitate itscomplete combustion in the combustion zone, for re-using the unignitedor partially burned portions of the fuel which would otherwise pass toexhaust and into the atmosphere, and for reducing the oxides of nitrogenemitted from the exhaust system into the atmosphere. It has been foundthat approximately 15 to 20 percent exhaust gas recycling is required atmoderate engine loads to substantially reduce the nitrogen oxide contentof the exhaust gases discharged in the atmosphere, that is, to belowabout 1,000 parts per million.

[0021] Although the prior art systems have had the desired effect ofreducing nitrogen oxides in the exhaust by reducing the maximumcombustion temperature as a consequence of diluting the fuel-air mixturewith recycled exhaust gases during certain operating conditions of theengine, these systems have not been commercially acceptable from thestandpoints of both cost and operating efficiency and have beencomplicated by the accumulation of gummy deposits which tend to clog therestricted bypass conduit provided for recycling the exhaust, and havealso been complicated by the desirability of reducing the recyclingduring conditions of both engine idling when nitrogen oxide emission isa minor problem and wide open throttle when maximum power is required,while progressively increasing the recycling of exhaust gases withincreasing engine load at part open throttle.

[0022] The nitrogen oxide emission is a direct function of combustiontemperature, and for that reason is less critical during engine idlingwhen the rate of fuel combustion and the consequent combustiontemperature are minimal but tends to be problematic during throttle upand extended full speed operation. In the usual hydrocarbon fuel typeengine, fuel combustion can take place at about 1,200° F. The formationof nitrogen oxides does not become particularly objectionable until thecombustion temperature exceeds about 2,200° F., but the usual enginecombustion temperature, which increases with engine load or the rate ofacceleration at any given speed frequently, rises to about 2,500° F. Itis known that the recycling of at least one-twentieth and not more thanone-fourth of the total exhaust gases through the engine, depending onthe load or power demand, will reduce the combustion temperature to lessthan 2,200° F. Contaminants in the exhaust resulting from fuel additivesdesired for improved combustion characteristics normally exist in agaseous state at combustion temperatures exceeding about 1,700° F., buttend to condense and leave a gummy residue that is particularlyobjectionable at the location of metering orifices and valve seats inthe exhaust recycling or bypass conduit.

[0023] Thus, natural gas fired internal combustion driven co-generationsystems have previously suffered from one or more disadvantages.Specifically, the EGR system did not recycle exhaust gas to the intakeengine manifold at sufficiently low temperature to foster low cylinderhead temperatures. Simultaneously, turbo charged fuel systems, becauseof the compression, increased intake fuel manifold temperatures causingthe same affect. Additionally, engine-cooling systems were not efficientenough to remove substantial engine heat from the cooling fluid whilemaintaining an inlet temperature of the coolant sufficient to reducehead temperatures to an acceptable level. This in turn reduced the heat,which was transferred to the co-generation client. However, increasingcoolant flow through the engine increases parasitic load decreasingefficiency. The result was a rich burning engine, i.e. inefficient, withsubstantial thermal NO_(x) production, violating air emission standards,while not providing sufficient heat transfer to the process/heatco-generation loop to be worthwhile.

[0024] A further drawback was that recycling exhaust gas increased theintake air temperature and, therefore, increased the head temperature.This is particularly true when the inlet gas is supercharged. Thiscombination of disadvantages made natural gas fueled, internalcombustion driven co-generation systems an unacceptable candidate forclient based distributed generation complexes.

[0025] It would be, therefore, advantageous to have a system, whichreduced fuel consumption, as well as NO_(x) production while deliveringsubstantial heat to the process/utility heat co-generation system. Inaddition, it would be advantageous to run a lean burning engine usingrecycled exhaust gas, which results in not only a lean burn but alsoreduced head temperatures leading to reduces thermal emissions andgreater efficiency.

SUMMARY OF THE INVENTION

[0026] It has now been unexpectedly discovered that a system for enginecooling and effective heat transfer to a co-generation client, reducesengine head temperature thereby reducing fuel consumption and reducingpollutants, as well as delivering substantially increased heat to aco-generation process/utility heat facility. The cooling cycles andprocess/utility heat radiation configurations of the inventive systemmaintain cylinder inlet temperature resulting in improved efficiency,reduced thermal NO_(x) and longer engine life. This allows operation ofthe engine at optimum inlet and outlet temperatures regardless ofco-generation process/utility heat system requirements, withoutexcessive parasitic pump loads.

[0027] In accordance with the invention, a split flow engine coolingsystem includes a first coolant loop which directs coolant through theengine block, and a second loop which directs coolant through the atleast one exhaust manifold in cooperation with the first loop, such thatthe coolant inlet temperature of the first loop is substantially reducedto maintain appropriate engine head temperatures to reduce thermalNO_(x) while maintaining efficiency. The two loops then merge at aprocess heat exchanger such that the combined output heat contained inthe liquid of the two loops is effective to deliver increased heat tothe co-generation process/utility heat system without an increase inparasitic load, i.e. using the engine internal pump only.

[0028] Advantageously, the coolant loops each carry different quantitiesof coolant to assure engine performance. In one embodiment, the loopscan be balanced by means of a dynamic feed back valveing to assure headtemperatures within a specified range.

[0029] In accordance with another aspect of the instant invention, aturbo intercooler heat exchanger is used to reduce the temperature ofcompressed engine intake gas, emerging from the turbocharger, prior toits entry into the intake manifold of the engine such that the inlet gastemperature is reduced to retard the formation of thermal NO_(x). Thusthe engine driven coolant pump can be utilized exclusively for thecoolant loop, reducing the parasitic load, while drastically reducingcylinder inlet temperature resulting in improved efficiency, lowerthermal NO_(x) and longer engine life.

[0030] In another aspect an EGR cooling circuit using air finned heatexchangers is used to reduce the temperature of the recycled exhaustgas, prior to its mixing with the intake gases for combustion. Thisfurther reduces cylinder inlet temperature resulting in improvedefficiency, lower thermal NO_(x) and longer engine life.

[0031] In accordance with the invention a dump/balance radiator is usedto remove heat not transferred to the co-generation process/utility heatsystem such that engine efficiency is maintained even in the absence ofthe co-generation process/utility heat system load.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following drawings form part of the present specification andare included to further demonstrate certain embodiments. Theseembodiments may be better understood by reference to one or more ofthese drawings in combination with the detailed description of specificembodiments presented herein.

[0033]FIG. 1 is a flow chart of the heat transfer systems forco-generation of the instant invention;

[0034]FIG. 2 is a flow chart of the engine cooling loop of the heattransfer systems for co-generation of the instant invention;

[0035]FIG. 3 is a flow chart of the co-generation process/utility heatdelivery loop of the instant invention;

[0036]FIG. 4 is a flow chart of the turbocharger intercooler loop withturbo charged intake gas interface in accordance with the instantinvention; and,

[0037]FIG. 5 is a flow chart detail of the interface of the turbochargerintercooler radiator loop interface with the engine intake gas systemand the engine exhaust system including the exhaust recycle inaccordance with the instant invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] In accordance with the instant invention a natural gas fueled,internal combustion engine, employing exhaust gas recycle (EGR),delivers power to spin a coupled electric turbine, as well as heat ofcombustion, through a heat exchanger, to a co-generation process/utilityheat loop for on site use as heat for process water, utility heat, spaceheat, potable hot water and the like. This is accomplished with theinstant system by increasing the transfer of engine heat to theco-generation process/utility heat loop while maintaining the engine,and especially the head temperature low enough to increase efficiencyand reduce thermal NO_(x) to acceptable levels, even in the presence ofthe recycled exhaust gas. This is accomplished with substantially noincrease in parasitic power requirements, such as adding external pumpsto increase the flow through the heat exchanger.

[0039] In accordance with the invention an engine coolant loop flow issplit so that a first portion flows through the engine block, by way ofthe engine oil cooler, and through a thermal valve control to the fluidprocess heat exchanger. A second portion flows to at least one fluidcooled exhaust manifold by way of the engine oil cooler, for example,through the inlet ports of the left and right liquid cooled exhaustmanifolds and then the inlet port of the fluid cooled turbocharger whereit merges with the liquid from the first loop prior to going through thefluid process heat exchanger, which delivers heat to the co-generationprocess/utility heat system.

[0040] Thus, in accordance with one embodiment, the coolant flowsthrough a cooling loop by way of an engine driven pump through the oilheat exchanger. Exiting the oil heat exchanger it splits into twoparallel loops. One loop follows a path through the engine block and theother through the coolant manifold, and then the coolant cooledturbo-charger. Both coolant flow loops converge at the thermal controlvalve where they blend back together to form a single stream prior toflowing through the fluid process heat exchanger. The thermal controlvalve senses the blended stream temperature and by-passes the fluidprocess heat exchanger if the temperature is below the threshold engineblock inlet tempeture of, for example, 175° F. This closed loopprohibits flow through the fluid/process heat exchanger and dump/balanceradiator to retard heat loss until optimum engine block inlettemperature is achieved. When the temperature is greater than, forexample, 175° F., flow through the control valve is first divertedpartially to the fluid/process heat exchanger and then fully to thefluid/process heat exchanger as operating temperatures are reached.

[0041] The combined flow is, thus, through the coolant/process heatexchanger for use in heat exchange with the co-generationprocess/utility heat system. This parallel cooling loop increases theengine cooling loop heat available to the process/utility heat system,significantly, while maintaining favorable engine operating conditions.For example, the system of instant invention can maintain engine blockoutlet temperature of 198° F. instead of the typical 210° F. ofcomparable engine designs, while heat delivered to the process/utilityco-generation system increased from a typical 780,000 BTU/hour to1,100,000 BTU/hour. Flow through system is nominally 106 GPM with adifferential of 20° F. across the engine block. In this manner thecoolant through the second loop is at a higher tempeture, but a lowerflow rate, while the coolant through the first is at a slightly lowertempeture, but a higher flow rate to keep the cylinder heads cooler,thus, increasing efficiency and reducing thermal NO_(x) emissions.

[0042] In accordance with a further aspect, the system employs aseparate loop to cool supercharged engine inlet feed. This separation ofthe intercooler liquid coolant loop from the engine coolant loopprovides a separate heat exchanger upstream of the engine intakemanifold to reduce engine intake temperatures, drastically reducing headtemperatures within the engine. Likewise, in a further aspect theexhaust recycle gas is cooled by at least one air cooled radiator priorto admixing it with air and fuel which is then compressed in thesupercharger.

[0043] The power source compatible with the instant invention is anatural gas fueled, internal combustion liquid cooled engine, wherein atleast a portion of the exhaust gas is recycled to reduce NO_(x). Forexample a Deutz brand Engine Model BE 8 M 1015 GC engine manufactured byDeutz. The natural gas fired internal combustion engine is the primemover of the electrical generation system, having liquid coolant flowsystem required return coolant at a temperature to the engine to reducehead temperature to less than about 1800° F. The internal engine pumpmoves the coolant through the various engine components and then throughthe process heat exchanger to transfer heat to the co-generationprocess/utility the system.

[0044] Turning to the drawing, there is shown in FIG. 1, the system 10,in accordance with the instant invention. An engine block 12 containsfluid cooling ports through which cooling fluid travels by means ofinternal fluid pump 14 located upstream of oil heat exchanger 16, whichis ideally housed within the engine. As shown, oil heat exchanger 16 isin fluid communication with the inlet port of engine block 12 by meansof conduit 18 and with inlet of fluid cooled manifold 20 by means ofconduit 22. Preferably, oil heat exchanger 16 is contained within engineblock 12 and is an integral part thereof. The outlet of engine block 12communicates with the inlet of thermal control valve 24 by means ofconduit 26.

[0045] The outlet of fluid cooled manifold 20 communicates with theinlet of fluid cooled turbocharger manifold 28 by means of conduit 30.The outlet of fluid cooled turbocharger manifold 28 communicates with asecond inlet of thermal control 24 through conduit 22. In a bypasscircuit for engine warm up, the outlet of thermal control valve 24communicates through internal fluid pump 14 with oil heat exchanger 16through conduit 34. Alternately, during operation thermal control valve24 communicates through internal fluid pump 14 with oil heat exchanger16 by way of fluid process/heat exchanger 36 via conduit 38 anddump/balance radiator 40 via conduit 42 and then a T connect of conduit44 with conduit 34.

[0046] As better seen in FIG. 2, this fluid loop comprises the coolantsystem 11 of the present invention. In operation, internal fluid pump 14is driven by engine block 12 to flow coolant at a tempeture of about175° F. and a flow rate of about 106 GPM through oil heat exchanger 16and simultaneously through conduit 18 to the inlet of engine block 12 ata tempeture of about 182° F. and a flow rate of about 91 GPM and conduit22 at a tempeture of about 182° F. and a flow rate of about 26 GPM toinlet of exhaust-cooled manifolds 21.

[0047] The exhaust-cooled manifolds 21 comprise the initial fluid cooledmanifold 20 and the fluid cooled turbocharged manifold 28 as shown inFIG. 1., but can consist of one or more liquid cooled manifolds forremoving heat from the engine exhaust. In accordance with the invention,these manifolds may comprise a single unit as shown in FIG. 2 orseparate units shown in FIG. 1. The function of these manifolds is tocool exhaust and generate heat to the cooling fluid, which will betransferred to the co-generation client as described below.

[0048] Coolant exiting from exhaust-cooled manifold 21 at a tempeture ofabout 210° F. and a flow rate of about 26 GPM, flows to thermal controlvalve 24, which functions to limit fluid circulation back to inlet ofthe engine block 12 until operating temperature of the system isattained, and thereafter through conduit 38 to fluid process/heatexchanger 36. Coolant exiting from engine block 12 at a tempeture ofabout 198° F. and a flow rate of about 91 GPM, flows to thermal controlvalve 24 where is merges with the coolant from exhaust-cooled manifold21. Dump/balance radiator 40 serves as a cooling radiator for the systemto balance coolant inlet temperature to the oil heat exchanger 16 iffluid process/heat exchanger 36 removes insufficient heat or is turnedoff.

[0049] Returning to FIG. 1, fluid process/heat exchanger 36 is aradiator which allows heat transfer from coolant system 11 (see FIG. 2)to co-generation process/utility heat system 13, as seen in detail inFIG. 3. Co-generation process/utility system comprises a closed loop tocirculate fluid, which is heated in fluid process/heat exchanger 36, bymeans of pump 46. Fluid process/heat exchanger 36 communicates withprimary facility load 48 and secondary facility load 50 by means ofconduit 52 and return conduit 54.

[0050] In operation, fluid process/heat exchanger 36 which containscoolant fluid at a tempeture of about 206° F. at a flow rate of about106 GPM, provides heat exchange between coolant system 11 andco-generation process/utility heat system 13, which provides heatedliquid to the client in a co-generation configuration. Thus, theco-generation client receives transferred heat from the coolant system11 by way of fluid process/heat exchanger 36 to the co-generationprocess/utility heat system 13. The coolant in coolant system 11 is thenheat balanced, if necessary, in the dump/balance radiator 40 to returnthrough internal fluid pump 14 to oil heat exchanger 16 to loop at atempeture of about 175° F. at a flow rate of about 106 GPM.

[0051] Thus, for example heat in coolant flow, through thecoolant/process heat exchanger, is captured for the co-generation clientuse by counter flowing process/utility water flowing through thecoolant/process heat exchanger. Thermal regulating valves can be used toregulate process/utility water temperature to insure appropriate watertemperature delivery to the co-generation use.

[0052] In accordance with one aspect of the invention, an exhaust heatrecovery silencer 56, further cools the exhaust from the engine block 12and communicates through client absorption chiller 58 by means ofconduit 60 and return conduit 62, as will be further described below inreference to FIG. 5.

[0053] Turning to FIG. 4, a turbo intercooler cooling circuit is shownand its interface with recycled exhaust gas, fuel, and air. Turbointercooler cooling circuit comprises a turbo intercooler 68, which iscooled by coolant loop separate from coolant system 11 orprocess/utility heat system 13 and includes an intercooler radiator 70fluidly communicating, via conduit 72 and pump 74, in a continuousclosed circuit, through intercooler coil 76 of turbo intercooler 68.This fluid cooling system is dedicated to further reducing the inlettempeture of the compressed fuel/air/exhaust gas mixture from theturbocharger 78 as further explained below.

[0054] As better seen in FIG. 5, there are three operating systemsassociated with the intercooler radiator in accordance with the instantinvention. FIG. 5 shows the interfaces between the turbo intercoolercooling circuit, the turbocharged, or compressed inlet gas mixture tothe engine intake manifold and the recycled exhaust gas. Thisinteraction is important in that head temperatures, gas inlettemperatures, and exhaust gas recycle temperatures can be tuned.

[0055] As seen in FIG. 5, intercooler radiator 70, pump 74, and conduit72 continually circulate coolant, in a closed loop, through coil 76 ofturbo intercooler 68 as previously described and shown in FIG. 4.Ambient outside air passes through air filter 100 and intake conduit 102to EGR venturi 104, where air mixed with recycled exhaust gas fromconduit 180 as will be more fully described. Mixed air and exhaust gasexists EGR venturi 104 through intake conduit 106 into fuel/air venturi108 where the air exhaust gas mixture entrains fuel from a regulator(not shown). The fuel/air/exhaust gas mixture is compressed inturbocharger 78 via intake conduit 110. The compressed fuel/air/recycledexhaust gas mixture exists turbocharger 78 through intake conduit 80into turbo cooler 68 where it is cooled from 400° F. to 165° F. Thecooled intake gas exists turbo intercooler 68 into engine intakemanifold 112 and into engine cylinders 82 via conduit 84. Exhaust gasfrom engine cylinders 82 exits into fluid cooled manifold 21 aspreviously described in FIG. 2 and enters turbocharger 78 throughexhaust conduit 114 to power the turbocharger 78, thus compressing thefuel/air/recycled exhaust gas mixture entering turbocharger 78 by meansof intake conduit 110 as previously described.

[0056] As can be seen, exhaust gas exiting turbocharger 78 is split intoa recycled stream and an exhaust stream. The exhaust stream 116 entersthree-way catalyst 118 and then exhaust heat recovery silencer 56 aspreviously described in connection with the description of FIG. 1. Itwill be realized, by one skilled in the art, that the exhaust heatrecovery silencer 56 is on the co-generation process/utility heat system13 and provides additional heat recovery for that system.

[0057] A portion of the exhaust gas to be recycled passes throughconduit 120 to primary air cooled EGR cooler 122; and, if necessary,secondary air cooled EGR cooler 124 by means of conduit 126 and thenpasses into EGR venturi 104 through conduit 180 as previously described.

[0058] Thus, in accordance with the invention, ambient air (70° F.)flows through air filter to EGR venturi where it is mixed with up to 20%cooled exhaust gas (140° F.) at 100% load. The percent of recycledexhaust gas utilized is a function of engine load. This mixture (120°F.) then passes through the fuel/air venturi where fuel is drawn from azero pressure gas regulator and mixed with the ambient air & exhaust gasto be flowed to the ambient side of the turbocharger. Thefuel/air/recycle exhaust gas mixture is then pressurized by an exhaustgas-powered turbine to a pressure of 15 psig of at a temperature of(400° F.) This pressurized mixture passes through the turbochargerintercooler which reduces the pressurized and high temperature mixtureto about 165° F. to be introduced into the intake manifold and then tothe engine cylinders.

[0059] Following combustion, exhaust gas from the cylinders (1100° F.)passes through the coolant-cooled manifolds to recover heat, whichreduces the exhaust gas tempeture to about 940° F. The exit exhaust gasenters the exhaust (turbine driving section) of the turbocharger and,upon exiting, passes through a “T” with about 80% of the gas beingflowed through a catalyst and a heat recovery silencer or muffler aspreviously described, and exhausted to atmosphere. A second portioncomprising about 20% of the exhaust gas is passed through air coolers aspreviously described to the EGR venturi for introduction to the air/fuelintake system. The recycled exhaust gas is cooled by the air coolers toabout 140° F. prior to admixing with air in the EGR venturi.

[0060] The foregoing discussions, and examples, describe only specificembodiments of the present invention. It should be understood that anumber of changes might be made, without departing from its essence. Inthis regard, it is intended that such changes—to the extent that theyachieve substantially the same result, in substantially the same way—would still fall within the scope and spirit of the present invention.

1. A heat transfer and cooling system for a natural gas fueled, internalcombustion engine driven co-generation unit utilizing recycled exhaustgas comprising: (a) a fluid system for cooling said internal combustionengine having a first loop containing a cooling fluid which fluidlycommunicates with the cooling ports of said internal combustion engineat a first inlet temperature and a first flow rate; and, a second loopcontaining a cooling fluid which fluidly communicates with the coolingports of at least one exhaust manifold of said internal combustionengine at a second inlet temperature and a second flow rate, wherein thecooling fluid exiting said first loop at the first exit temperature andthe cooling fluid exiting said at the second exit temperatures econdloop converge in a confluence at in at least one process heat exchanger;and; (b) a co-generation process/utility heat loop containing a heatreceiving medium and in communication with said at least one processheat exchanger containing said confluence such that heat contained insaid confluence from said cooling system is passed to the media of saidco-generation process/utility heat loop.
 2. The heat transfer andcooling system of claim 1 wherein said fluid system further comprises atleast one dump/balance radiator in fluid communication with said atleast one process heat exchanger to remove heat from said cooling fluidprior to the return of the cooling system fluid to said engine.
 3. Theheat transfer and cooling system of claim 1 wherein said fluid systemfurther comprises an oil heat exchanger in fluid communication with anengine coolant pump on an oil heat exchanger inlet and is in fluidcommunication each one of said two loops on an oil heat exchangeroutlet.
 4. The heat transfer and cooling system of claim 1 wherein saidfluid system further comprises a thermal control valve which fluidlycommunicates on an inlet side of said thermal control valve with saidconfluence and fluidly communicates on an outlet side of said thermalcontrol valve with said at least one process heat exchanger or said oilheat exchanger depending on the temperature of said confluence.
 5. Theheat transfer and cooling system of claim 1 further comprising a turbointercooler unit for cooling compressed air/recycle exhaust gas/fuelintake admixture prior to said admixture entering an engine intakemanifold.
 6. The heat transfer and cooling system of claim 5 whereinsaid turbo intercooler unit comprises a fluid coolant cooled intercoolercoil for cooling a compressed air/recycle exhaust gas/fuel intakeadmixture, which is in liquid communication with an intercooler radiatorfor exhausting heat from said fluid coolant and a circulation pump forcirculating said fluid coolant.
 7. The heat transfer and cooling systemof claim 1 further comprising at least one exhaust gas recycle coolerfor cooling the recycled exhaust gas prior to forming an air/recycleexhaust gas/fuel intake admixture.
 8. The heat transfer and coolingsystem of claim 7 wherein said at least one exhaust gas recycle coolerfor cooling the recycled exhaust gas prior to forming an air/recycleexhaust gas/fuel intake admixture comprises two air cooled units inseries.
 9. The heat transfer and cooling system of claim 1 wherein saidat least one exhaust manifold of said internal combustion enginecomprises two exhaust manifolds, wherein a first manifold is in heatexchange communication with exhaust ports of said engine and the secondmanifold is in communication with exhaust exiting a turbocharger. 10.The heat transfer and cooling system of claim 1 wherein saidco-generation process/utility heat loop further comprises a clientabsorption chiller in fluid communication with an exhaust heat recoverydevice such that non recycled engine exhaust is passed through saidexhaust heat recovery device to transfer heat in the non recycled engineexhaust by way of the client absorption chiller to said co-generationprocess/utility heat loop.
 11. A method for increasing the transfer ofheat to a process/utility heat loop from a liquid cooling system forefficiently cooling a natural gas fueled, internal combustion engineutilizing recycled exhaust gas for driving a co-generation unitcomprising: (a) circulating a cooling fluid for cooling said internalcombustion engine through a first loop which fluidly communicates withcooling ports of said internal combustion engine at a first inlettemperature and at a first flow rate; and, through a second loopcontaining a cooling fluid which fluidly communicates with cooling portsof at least one exhaust manifold of said internal combustion engine at asecond inlet temperature and at a second flow rate, such that thecooling fluid exiting said first loop at a first exit temperature andthe cooling fluid exiting said second loop at a second exit temperatureconverge in a confluence in least one heat exchangers; and (b)circulating a heat exchange media in a cooling a co-generationprocess/utility heat loop in communication with said at least oneprocess heat exchanger containing said confluence from said coolingsystem such that heat contained in said confluence from said coolingsystem is passed to the media of said co-generation process/utility heatloop.
 12. The method of claim 11 wherein said cooling fluid is furtherpassed though at least one dump balance radiator dump/balance radiatorin fluid communication with said at least one process heat exchanger toremove heat from said cooling system prior to the return of the coolingfluid to said engine.
 13. The method of claim 11 wherein said coolingfluid is further passed though an oil heat exchanger in fluidcommunication with the an engine coolant pump on an oil heat exchangerinlet and is in fluid communication each one of said two loops on an oilheat exchanger outlet.
 14. The method of claim 11 wherein said coolingfluid is further passed through a thermal control valve which fluidlycommunicates on an inlet side of said thermal control valve with saidconfluence and fluidly communicates on an outlet side of said thermalcontrol valve with said at least one process heat exchanger or said oilheat exchanger depending on the temperature of said confluence.
 15. Themethod of claim 11 comprising the further step of passing cooling fluidthrough a turbo intercooler third loop, which is not in liquidcommunication with said first or said second loop, for cooling acompressed air/recycle exhaust gas/fuel intake admixture prior to saidadmixture entering the an engine intake manifold.
 16. The method ofclaim 15 wherein said turbo intercooler loop comprises a fluid coolantcooled intercooler coil for cooling compressed air/recycle exhaustgas/fuel intake admixture which is in liquid communication with anintercooler radiator for exhausting heat from said fluid coolant and acirculation pump for circulating said fluid coolant.
 17. The method ofclaim 11 comprising the further step of cooling the recycled exhaust gasprior to forming an air/recycle exhaust gas/fuel intake admixture 18.The method of claim 17 wherein said cooling step comprises passing saidrecycle exhaust gas through two air cooled units in series prior toforming said air/recycle exhaust gas/fuel intake admixture.
 19. Themethod of claim 11 wherein said at least one exhaust manifold of saidinternal combustion engine comprises two exhaust manifolds, wherein afirst manifold is in heat exchange communication with exhaust ports ofsaid engine and the second manifold is in communication with exhaustexiting a turbocharger.
 20. A heat transfer and cooling system for anatural gas fueled, internal combustion engine driven co-generation unithaving a turbocharger and utilizing recycled exhaust gas comprising: (a)a fluid cooling system for cooling said internal combustion enginehaving a cooling fluid, an engine coolant pump for flowing said coolingfluid through said fluid cooling system, an oil heat exchanger forremoving heat from the engine oil in cooling fluid communication with anoutlet of said engine coolant pump and an outlet cooling fluidcommunication each one of two loops wherein a first loop cooling fluidlycommunicates with cooling ports of said internal combustion engine at afirst inlet temperature at a first flow rate; and, a second loop coolingfluidly communicates with an intake of a first exhaust manifold which isin heat exchange communication with engine exhaust ports and then asecond exhaust manifold in heat exchange communication with exhaustexiting said turbocharger at a second inlet temperature at a second flowrate, wherein the cooling fluid exiting said first loop at a first exittemperature and a first flow rate and the cooling fluid exiting saidsecond loop at a second exit temperature and a second flow rate convergein a confluence at an inlet side of a thermal control valve whichcooling fluidly communicates on the an outlet side of said thermalcontrol valve with at least one process heat exchanger or said oil heatexchanger depending on the temperature of said confluence and said atleast one process heat exchanger fluidly communicates with at least onedump/balance radiator to remove heat from said cooling system prior tothe return of the cooling system fluid to said engine; (b) aco-generation process/utility heat loop containing a heat receivingmedium in communication with said at least one process heat exchangercontaining said confluence from said cooling system such that heatcontained in said confluence from said cooling system is passed to themedia of said co-generation process/utility heat loop; (c) a turbointercooler unit for cooling compressed air/recycle exhaust gas/fuelintake admixture prior to said admixture entering an engine intakemanifold comprising a fluid coolant cooled intercooler coil for coolingsaid compressed air/recycle exhaust gas/fuel intake admixture which isin liquid communication with an intercooler radiator for exhausting heatfrom said fluid coolant and a circulation pump for circulating saidfluid coolant; (d) at least one exhaust gas recycle cooler for coolingthe recycled exhaust gas prior to forming the compressed air/recycleexhaust gas/fuel intake admixture comprising two air cooled units inseries; and, (e) an absorption chiller in fluid communication with anexhaust heat recovery device such that non recycled engine exhaust ispassed through said exhaust heat recovery device to transfer heat in thenon recycled engine exhaust by way of the client absorption chiller tosaid co-generation process/utility heat loop.